Method and apparatus for forming three-dimensional laminated product from photo-curable liquid

ABSTRACT

A three-dimensional laminated product forming apparatus and method for forming a three-dimensional laminated product from a photo-curable liquid by progressively superposing solid laminae one on top of another by photo-curing a surface layer of the photo-curable liquid and converting it to a solid lamina. A product table is provided on which a three-dimensional solid product is built up in progressive steps and which is incrementally advanced into the photo-curable liquid by a specified depth each step. A liquid surface leveling device works as a capillary to draw up a photo-curable liquid by capillary action while it is in contact with the surface of the photo-curable liquid contained in the container. The device is moved over the surface of the photo-curable liquid to apply the collected photo-curable liquid over a three-dimensional laminated product being partly built up on a product table to form a uniform thickness of a surface layer of the photo-curable liquid with a surface leveled and smoothed over the three-dimensional laminated product being partly built up. An irradiating head forms a beam spot of reactive stimulation on the surface to cure the surface layer and convert it to a solid lamina on the three-dimensional laminated product being partly built up as the three-dimensional laminated product.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and an apparatus forforming a three-dimensional laminated product, such as, a model or coreuseful for investment casting of an intended ornamental jewelry craftproduct.

[0003] 2. Description of the Related Art

[0004] In recent years, it has been known to form a three-dimensionalproduct by successively superposing a number of photo-cured laminae ofstratified cross sections of the three-dimensional product one on thetop of another. Specifically, a photo-cured lamina is formed onpreviously photo-cured laminae by scanning and curing a specifiedthickness of surface layer of a photo-curable liquid by laser energy,building up the three-dimensional product. One of such methods andapparatus for forming three-dimensional products from a photo-curableliquid is known from, for instance, Japanese Unexamined PatentPublication No. 56-144478.

[0005] In order to introduce a fresh liquid of a quantity necessary toprovide a specified thickness of surface layer of the photo-curableliquid, which will to be formed as a photo-cured lamina on thepreviously superposed photo-cured laminae, the under-building productneeds to be moved precisely by a distance equal to the specifiedthickness in progress steps away from the working surface level of thephoto-curable liquid at which a surface layer of the fresh liquid isirradiated with laser energy. In practice this has proven difficult. Forexample, for forming the surface layer of the photo-curable liquid witha precisely controlled thickness, as described in, for instance,European Patent Specifications EP.0171069B1 and EP 0535720B1, theunder-building product is initially moved down away from the specifiedworking surface to a level beyond the specified working surface level,and then, moved back to the specified working surface level in order toaccomplish each stepwise adjustment during the process of making thearticle being built. Alternatively, as described in, for instance,Japanese patents Nos. 26195445 and 2715649, a fresh liquid spraymechanism is provided to spray a fresh liquid so as to form a precisethickness of surface layer of a photo-curable liquid on anunder-building product after moving down the under-building product awayfrom the specified working surface by a distance equal to the specifiedthickness.

[0006] While employing an initial increment of movement of the lastformed lamina away from the specified working surface to a level beyondthe specified working surface level enables the apparatus for building athree-dimensional product by photo-curing to be simple in constructionand mechanism and compact in overall size, however, it causes a somewhattangled problem of spending a long time before completely building athree-dimensional product. That is, the photo-curable liquid is governedin fluidity by its relatively high viscosity and surface tension, andtherefore, a relatively long time is required to introduce a preciselycontrolled quantity of the fresh liquid for providing a specifiedthickness of surface layer of the photo-curable liquid for the nextprocessing step. In addition to a long time that is spent beforeintroduction of a precisely controlled quantity of the fresh liquid, atime is required to move back the working surface to the specifiedworking surface level after the introduction of a precisely controlledquantity of the fresh liquid. Further, application of laser energy ontoa surface layer of the photo-curable liquid must wait for a time untilthe surface layer is entirely leveled. In consequence, a long workingtime is necessary to complete a single photo-cured lamina, which causesa rise in manufacturing costs. Since the photo-curable liquid transformsfrom a fluid to a solid by means of photochemical reaction, such as, aradical reaction and a cationic reaction, the photo-curable liquiditself has a somewhat restricted effective life, which causes a largequantity of photo-curable liquid of no direct use, and hence leads to arise in manufacturing costs.

[0007] On the other hand, while spraying a fresh liquid by means of thefresh liquid spray mechanism to form a precise thickness of surfacelayer of a photo-curable liquid on an under-building product reduces atime required to introduce a precisely controlled quantity of the freshliquid and level a surface layer, and realizes miniaturization of afluid container in which the photo-curable liquid is accommodated, thefresh liquid spray mechanism has to be equipped not only with variousassociated parts such as a nozzle, mesh screen, a rotary shaft, a brushand a water wheel which makes the apparatus bulky, but also a secondaryfluid container in which a photo-curable liquid to be sprayed must beprovided. Further, there is the necessity of installing a surface leveladjusting mechanism for adjusting a level of the surface layer afterspraying a fresh liquid. Such a surface level adjusting mechanism iscomplicated in structure and expensive, which leads to a rise inmanufacturing costs.

SUMMARY OF THE INVENTION

[0008] It is a primary object of the invention to provide a method anapparatus for forming a three-dimensional laminated product from aphoto-curable liquid by step-wise photo-curing of laminae.

[0009] Another object of the invention is to provide a three-dimensionallaminated product forming apparatus equipped with a liquid surfaceleveling device working as a capillary which draws up a reserve ofphoto-curable liquid therein and applies it over a laminated productthat is being built up so as to form a uniform thickness of a surfacelayer of the photo-curable liquid with a working surface leveled andsmoothed.

[0010] The foregoing objects are accomplished by providing athree-dimensional laminated product forming method and apparatus forforming a three-dimensional laminated product from a photo-curableliquid by progressively superposing solid laminae having a specifiedthickness, one on top of another, each solid lamina being provided byphoto-curing a surface layer of the photo-curable liquid and convertingit to a solid lamina. The three-dimensional laminated product formingapparatus comprises a product table on which a three-dimensional solidproduct is built up in progressive steps, said product table beingsunken in a reservoir of photo-curable liquid by a distance equal to thespecified thickness of the solid lamina in each said step; and a liquidsurface leveling device which works with a capillary effect to collector draw up a reserve of photo-curable liquid while it is in contact withthe surface of the photo-curable liquid contained in a container whichis placed on a container table. The leveling device is moved over thesurface of the photo-curable liquid to apply the collected photo-curableliquid over a three-dimensional laminated product, that has been partlybuilt up on a product table and stepped down for the next lamina, so asto form a uniform thickness of a surface layer of the photo-curableliquid with a surface leveled and smoothed over the three-dimensionallaminated product that has been partly built up. An irradiating headforms a beam spot of reactive stimulation (ultraviolet energy) on thesmoothed and leveled surface layer of the photo-curable liquid so asthereby to cure the surface layer, and convert it to a solid laminasuperposing on the three-dimensional laminated product that is partlybuilt up as the three-dimensional laminated product.

[0011] According to the three-dimensional solid product formingapparatus and method, it is enabled to form a specified thickness of asurface layer of a photo-curable liquid over a three-dimensional producthaving been partly building up. The surface layer leveling devicecomprises a pair of surface leveling blades having an entrance that isset for a predetermined opening so that it is arranged as to work as acapillary. The structure is simple and the driving mechanism for it isalso simple and inexpensive. As a result, the three-dimensional solidproduct forming apparatus is made small in overall size, operatesquickly and is provided at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing and other objects and features of the inventionwill be made clear when reading the following description in accordancewith a preferred embodiment thereof in conjunction with the accompanyingdrawings in which:

[0013]FIG. 1 is a side view partly broken away of a three-dimensionallaminated product forming apparatus in accordance with a preferredembodiment of the invention;

[0014]FIG. 2A is a front view of a liquid surface layer leveling unitthat is installed in the three-dimensional laminated product formingapparatus shown in FIG. 1;

[0015]FIG. 2B is a side view of the liquid surface layer leveling unitthat is installed in the three-dimensional laminated product formingapparatus shown in FIG. 1;

[0016]FIG. 3 is a side view of a liquid surface leveling device of theliquid surface layer leveling unit shown in FIGS. 2A and 2B;

[0017]FIGS. 4A, 4B and 4C are front, top and cross-sectional views of aring model designed by CAD, respectively;

[0018]FIGS. 5A and 5B are explanatory top and cross-sectional views ofpart of a three-dimensional laminated product that is being built up byphoto-curing; and

[0019] FIGS. 6A-6C are side schematic views showing various variants ofthe liquid surface leveling device shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Referring to the drawings in detail, in particular, to FIG. 1which shows a computer controlled laminate molding apparatus 100specialized for forming a three-dimensional laminated product, such as,a prototype of jewelry rings, from a photo-curable liquid byphoto-curing. The computer controlled laminate molding apparatus 100 hasa housing 2 provided with a stationary bottom platform 4 on which alaminated three-dimensional product building unit 200A is installed, anda stationary top platform 6 to which a photo-curing unit 200B isinstalled, both platforms being fixedly mounted to the housing 2. Thelaminated product building unit 200A includes a movable container table22 on which a container 26 filled with a photo-curable liquid PCL, suchas, a photo-curable resin, is placed, a movable product table 24 onwhich a three-dimensional laminated product is built up from thephoto-curable liquid PCL in the container 26, and a liquid surface layerleveling unit 28 which is detachably mounted on the movable containertable 22. The movable container table 22 is guided on a guide post 22 bfixedly supported on the stationary platform 4 and moved up and down ina vertical direction by a vertical position control mechanism 22 a toadjust a vertical position of the container 26, and hence, inparticular, a vertical position of the top surface of the photo-curableliquid PCL in the container 26, when required. The movable product table24 is guided on guide post 24 b and moved down by a vertical positionshift mechanism 24 a so as to shift a working surface of the topphoto-cured laminae in vertical position. The term “working surface”used herein shall mean and refer to the surface of liquid at which aspot of reactive stimulation is focused on the photo-curable liquid tocure the photo-curable liquid and convert it to a solid material. Theworking surface is adjusted incrementally at a specified level byshifting down the movable product table 24 in steps by a verticaldistance of preferably from approximately 30 to approximately 70microns, that is, substantially equal to a predetermined thickness ofsurface layer of the photo-curable liquid is to be cured and convertedto a solid lamina over a solid body consisting of photo-cured laminaethat form part of a desired final three-dimensional laminated product.The liquid surface layer leveling unit 28, which will be described indetail later in connection with FIG. 2, develops and forms precisely thespecified thickness of surface layer of the photo-curable liquid overthe solid body consisting of photo-cured laminae that form part of thedesired three-dimensional laminated product that is being built up fromthe photo-curable liquid PCL.

[0021] The photo-curable resin employed as the photo-curable liquid PCLin the preferred embodiment of the invention has a composition such thatit can be cured by ultraviolet energy of less than 400 nm wave length.Many such compositions are known to those skilled in the art, and thecomposition may consist, for example, of acrylate resins and/or epoxyresins. For purposes of the present invention, the photo-curable liquidPCL needs to have a specific gravity of about 1.2, a viscosity of about1.4 Pa·S and a molecular weight of from about 200 to about 700. Thecomposition may also include a hardener and/or a photo-curing initiator,as are known, and is of generally low viscosity and a relatively highshrinkage rate.

[0022] The photo-curing unit 200B includes a beam irradiation focussinghead 32 for applying a spot of reactive stimulation, such as, an He—Cdlaser having a wavelength of 320 nm, to the photo-curable liquid PCL ata specified working surface, an X-Y position control mechanism such asan X-Y digital plotter 34 that moves the beam irradiation head 32 in twohorizontal directions intersecting each other, and a laser light source36. In the preferred embodiment, a multiple mode type of laser is usedthat has a wavelength of 325 nm and generates 5 to 10 mW output. In thecase where a three-dimensional laminated product has a minute shape, itis preferable to employ a single mode type of laser having 3 to 10 mWoutput which is easily focused since it does not encounter waveformdisorder. Laser rays generated by the light source 36 are transmitted tothe beam irradiation head 32 by way of light guide means 38 and focusedas a beam spot on the photo-curable photo medium PCL at the workingsurface. In order to transmit the laser rays with a high efficiency, andin a high level of safety, the light guide device employs a step-indextype of optical fiber 38 a and a flexible metal tube 38 b in which theoptical fiber 38 a is protected. Because the step index type of opticalfiber has apprehensions of causing waveform disorder due to repeatedinternal refraction of laser rays in the optical fiber and causingdiffusion of laser rays after an exit end of the optical fiber, in thecase of a minutely shaped three-dimensional laminated product, a singlestep index type of optical fiber, or otherwise a grated index type ofoptical fiber, may be preferably employed. In order to applyphoto-curing laser energy generated by the laser source 36 onto asurface layer of the photo-curable liquid PCL, the light source 36 isprovided with a plurality of high speed mechanical shutters (not shown)which are controlled in operation by actuators so as to admit laserenergy to enter the optical fiber and shut off it from entering theoptical fiber. In order to provide a laser beam of sufficient strengthfor curing a surface layer of the photo-curing liquid, the beamirradiation head 32 is provided with a focusing lens (not shown)operative to form a specified diameter of laser beam spot on the surfacelayer of the photo-curable liquid. The laser beam spot has a diameter ofapproximately 80 microns and a radiation strength of approximately 200W/cm² at the working surface which is sufficient to cure a predeterminedthickness of surface layer of the photo-curable liquid PCL. The workingsurface level is monitored by means or surface level sensor 30.Accordingly, the working surface level the working surface of thephoto-curable liquid PCL is adjusted at a specified level with respectto the beam irradiation head 32 by moving up or down the movablecontainer table 22.

[0023] Referring to FIGS. 2A and 2B, the surface layer leveling unit 28includes a liquid surface leveling device 50 that is driven in adirection X or the reverse direction Y by means of a drive mechanism 60to level the surface layer of the photo-curable liquid PCL, as will bedescribed in detail later. The liquid surface leveling device 50comprises a pair of leveling blades 52 and an attachment 54 to which theleveling blades 52 are detachably secured at opposite sides by setscrews 54 a. The attachment 54 is an integral part of a blade mount beam56. The drive mechanism 60 includes a pair of movable blade supports 62on which the blade mount beam 56 is supported. Each blade support 62comprises a base block 64 to which a pair of L-shaped support members 66are secured by set screws 66 a so as to form a space 66 b therebetweenfor receiving the blade mount beam 56. The blade support 62 is providedwith a blade adjustment screw 65 for adjusting a vertical level of theleveling blades 52 with respect to the working surface of thephoto-curable liquid PCL. The base block 64 at its lower portion isprovided with a guide slider 68 which slides on a guide rail 70 securedto an upright side wall 72 detachably secured to the container table 22.The blade support 62 is integrally formed with an arm 63 extendinginwardly from the base block 64. The drive mechanism 60 further includesa reversible motor 80 secured to the container table 22. As shown inFIG. 2B, the upright side walls 72 at their opposite end portionssupport a drive shaft 82 a and an idle shaft 82 b. The motor 80 isconnected to the drive shaft 82 a by a belt 80 a to transmit rotation ofthe motor 80 to the drive shaft 82 a. Two timing belt 84 are mountedbetween the drive shaft 82 a and the idle shaft 82 b with appropriatetension. The arms 63 of the blade supports 62 are secured to the timingbelts 84, respectively. When the motor 80 is actuated to rotate in ancounterclockwise direction as viewed in FIG. 2B, the blade supports 62with the liquid surface leveling device 50 supported thereby are movedin a direction X along the guide rail 70. On the other hand, when themotor 80 is reversed to rotate in a clockwise direction as viewed inFIG. 2B, the blade supports 62 with the liquid surface leveling device50 supported thereby are moved back in a reverse direction Y along theguide rail 70.

[0024] The drive mechanism 60 further includes position limiting means90 comprising a leg member 90 a secured to the base block 64 of theblade support 62, a stationary limit sensor 90 b secured to a guide rail90 d that is installed to the upright side wall 72, and a movable limitsensor 90 c mounted on the guide rail 90 d for slide movement. Each ofthe limit sensors 90 b and 90 c is operative to stop the motor 80 whendetecting the leg member 90 a. By sliding the movable limit sensor 90 c,the extent of movement of the surface layer leveling unit 28 isregulated.

[0025]FIG. 3 shows the liquid surface leveling device 50 in detail byway of example. The liquid surface leveling device 50 includes a pair ofthe leveling blades 52 which are secured to the attachment 54 by the setscrews 54 a and separated at their distal edges by a separation of, forexample, preferably approximately one (1) mm from each other so as toform therebetween a narrow 1 mm space 51 a that provides the levelingblades 52 with a capillary action. When the liquid surface levelingdevice 50 is moved down until the leveling blades 52 at their lowerdistal edges are brought into contact with the surface of thephoto-curable liquid PCL, the leveling blades 52, because of theirspacing and construction, work as a capillary to draw up thephoto-curable liquid PCL into the space 51 a by the aid of surfacetension of the photo-curable liquid PCL to establish a small reservoirof PCL liquid above the gap 51 a, as shown in FIG. 3. Since when theproduct table 24 is stepped down below the photo-curable liquid by adistance equal to the specified thickness of one cross-sectional stratumof the three-dimensional solid product, the surface of the photo-curableliquid does not always flow and cover evenly over the three-dimensionallaminated product that is being built up due to the surface tension,liquidity and viscosity of the photo-curable liquid. Consequently, whenthe liquid surface leveling device 50 moves in one of the directions Xand Y with the leveling blades 52 at their lower distal edges remainingin contact with the liquid surface, the collected reserve ofphoto-curable liquid is drawn and flows out from the space 51 a betweenthe leveling blades 52 to flow and cover over the three-dimensionallaminated product LP, thereby immediately forming a surface layer of thephoto-cured liquid having the specified thickness ready forphoto-curing. While the liquid surface leveling device 50 moves, theleveling blades 52 at their lower distal edges smooths and levels thesurface of the photo-curable liquid to form a uniform thickness of asurface layer over the three-dimensional laminated product, so as toenable immediate cure of the surface layer and conversion to a solidlamina having the specified thickness.

[0026] The three-dimensional solid product building unit 200A andphoto-curing unit 200B are numerically controlled in operation inaccordance with three-dimensional data of a design of athree-dimensional solid product provided by the aid of a computer system300. Such systems are well known to those skilled in the art.

[0027] The following description will be directed to the process ofproducing a three-dimensional solid product which is formed by themethod and apparatus of the invention and used as a model for producinga mold for casting rings by way of example.

[0028] Referring to FIGS. 4A-4C which are side, plane andcross-sectional views of a model M that is three-dimensionally designedby the computer system 300 by the use of a known modeling program, CADdata is translated into CAM data which is three-dimensional numericaldata of specified angular positions of points (P1, P2, . . . Px) ofinner and outer contours Ma and Mb for a number of cross-sectionalstrata of the model M.

[0029] As shown in FIG. 5A and 5B, when the three-dimensional solidproduct producing process is started according to the CAM data, themovable table 24 is moved down until it sinks into the photo-curableliquid PCL away from the working surface WS by a distance which is equalto the specified thickness of cross-sectional strata of the model T, andthen the movable container table 22 is moved up or down according to asignal provided by the surface level sensor 30 so as to position theworking surface WS of the photo-curable liquid PCL at the specifiedlevel with respect to the beam irradiation head 32 and subsequently, theliquid surface leveling unit 28 is moved over the working surface WS ofthe photo-curable liquid PCL to form a surface layer and smooth over thesurface layer. Subsequently, the X-Y digital plotter 34 is controlled bythe computer 300 to move the beam irradiation head 32 according to theCAM data. Immediately when the X-Y digital plotter 34 moves to locatethe beam spot BS in a position P(1)1 on the working surface WS, theshutter is opened. Thereafter, the X-Y plotter 34 moves linearly to passthrough positions P(1)2 . . . P(1)X at a constant speed betweenapproximately 300 mm/min and 1,000 mm/min, desirably at a constant speedof 800 mm/min, to scan the surface of the photo-curable liquid PCL alonga polygonal track. As a result, the area of the surface layer of thephoto-curable liquid PCL that is traversed by the beam is progressivelycured in the form of a polygon, which is almost similar to a circle,having a width equal to the diameter of the beam spot BS and convertedto a polygon-shaped solid loop having the same thickness as thespecified thickness of the cross-sectional stratum Ln of the model M.The polygonal solid loop LMa-1 forms an inner contour Ma of the firstfor the first cross-sectional strata L1 of the model M. As soon as thebean spot BS reaches the starting position P(1)1 passing through aposition P-(1)X, the shutter is closed. Subsequently, the X-Y digitalplotter 34 is moved outwardly to shift the beam irradiation head 32 by adistance equal to the diameter of the beam spot BS on the workingsurface WS, and the shutter is opened. Thereafter, the X-Y plotter 34moves linearly to pass through positions P(1)2 . . . P(1)X at theconstant speed to scan the working surface WS of the photo-curableliquid PCL, so as thereby to progressively cure the surface layer of thephoto-curable liquid PCL in the form of a polygon having the same widthas the diameter of the beam spot BS and convert it to a polygon-shapedsolid loop having the same thickness as the specified thickness of thecross- sectional stratum L of the model M. The polygonal solid loop LMb1forms an outer contour Mb of the first for the first cross-sectionalstrata L1 of the model M. These polygonal solid loops Lma1 and LMb1constitute a first solid lamina equivalent to the first cross-sectionalstrata L1 of the model M.

[0030] When the beam spot BS reaches the starting position P(1)1, andthe shutter is closed, the movable table 24 is moved down until the topsurface of the polygonal solid loops LMa1 and LMb1 as a solid laminasinks into the photo-curable liquid PCL away from the working surface WSby the same distance as the specified thickness T of cross-sectionalstrata of the model M. At this time, the movable container table 22 maybe moved up or down according to a signal provided by the surface levelsensor 30 so as to position the working surface WS of the photo-curableliquid PCL at the specified level with respect to the beam irradiationhead 32, if some adjustment is necessary. Subsequently, the liquidsurface leveling unit 28 is moved back over the working surface WS ofthe photo-curable liquid PCL to form a surface layer over the polygonalsolid loops LMa1 and LMb1 and smooth over the surface layer. In the samemanner as described above, the X-Y digital plotter 34 is moved to locatethe beam spot BS in a position P(2)1 over the working surface WS of thephoto-curable liquid PCL and smooth over the surface layer and scan thesurface of the photo-curable liquid PCL along a polygonal track, so asthereby to form polygonal solid loops Lma2 and is superposed LMb2 assecond solid lamina equivalent to the second cross-sectional strata L2of the model M over the previously formed first solid lamina. The sameprocess is progressively performed according to the CAM data to formpolygonal solid loops LMan and LMbn as solid laminae equivalent tocross-sectional stratum Ln of the model M.

[0031] By repeating the process the same times as the number ofcross-sectional stratum of the model M to superpose the same number ofpolygonal solid loops as the number of cross-sectional stratum of themodel M one top of the another, a three-dimensional laminated product isbuilt up as a mold for rings on the table 24. The entire surface spacebetween the inner and outer loops is solidified every 6 to 10 laminae togive structure to the product.

[0032] When the product has been completely built-up, it is removed fromthe table 24, and washed with ultrasonic cleaning for about 5 minutes toremove liquid resin. Use of ethanol and a detergent may also be requiredto remove the liquid resin. Next, the product or model is subjected tosecondary hardening under ultraviolet ray treatment, to solidify theentire model.

[0033] Various variants of the liquid surface leveling device 50 may beemployed as schematically shown in FIGS. 6A through 6C. Liquid surfaceleveling device 50 a shown in FIG. 6A comprises a pair of double walledleveling blades 52 a detachably secured to an attachment 54. Eachdouble-walled leveling blade 52 a consists of outer and inner wallsections separated at a constant distance to provide a crevice or gap 51b which works as a supplementary capillary. Further, the double-walledleveling blades 52 a are secured to the attachment 54 by set screws 54 aand separated at distal edges by a separation of, for example,preferably approximately 1 from each other to form therebetween a narrowspace 51 a which works as a primary capillary. When the double walledleveling blades 52 a are brought into contact with the surface ofphoto-curable liquid PCL, the liquid surface leveling device 50 a drawsup the photo-curable liquid PCL into the space 51 a and the crevice 51 bby the aid of its own capillary action and surface tension of thephoto-curable liquid PCL. This liquid surface leveling device 50 a ispreferable to draw up and hold a larger quantity of the photo-curableliquid PCL therein.

[0034]FIG. 6B shows another liquid surface leveling device 50 b whichcomprises a pair of surface leveling blades 52 b are secured to anattachment 54 by set screws 54 a and separated at lower distal edges bya separation of, for example, preferably approximately 1 from each otherto form therebetween a narrow space 51 b which works as a primarycapillary. Each surface leveling blade 52 b is formed with opposite endextensions 5 which is always positioned below the surface of thephoto-curable liquid PCL to draw up the photo-curable liquid PCL intothe space 51 b while the surface leveling blades 52 b are at least incontact with the surface of photo-curable liquid PCL. This liquidsurface leveling device 50 b is preferable to draw up the photo-curableliquid PCL and fill the space 51 b with it quickly.

[0035]FIG. 6C shows still another liquid surface leveling device 50 cwhich comprises a pair of surface leveling blades 52 c separated attheir distal edges by a specified separation of about 1 mm to formtherebetween a narrow space 51 c, and a porous pad 59, such as, a spongepad or a foam pad, is interposed between the surface leveling blades 52c with an effect of actively holding or retaining the photo-curableliquid drawn up by capillary action, and supplying it over a laminatedproduct that is being built up in the manner described. Further, thesurface level blades 51 c may themselves be made of porous material.

[0036] The liquid surface leveling device may take any form ofcombinations of the leveling blades 50, 50 a-50 c shown in FIGS. 3 and6A through 6 c.

[0037] While the present invention has been described in terms of apreferred embodiment, those skilled in the art recognize that thepresent invention can be practiced with various changes andmodifications without departing from the scope of the claims.

What is claimed is:
 1. A three-dimensional laminated product formingapparatus for forming a three-dimensional laminated product from aphoto-curable liquid by progressively superposing solid laminae having aspecified thickness one on top of another, each said solid lamina beingprovided by photo-curing a surface layer of the photo-curable liquid,said three-dimensional laminated product forming apparatus comprising: acontainer for holding a photo-curable liquid; a product table on which athree-dimensional laminated product is built up in progressive steps,said product table being positioned in said photo-curable liquid andadapted to be incrementally advanced into the container step by step,each step being a equal to a specified thickness for each solid lamina;a liquid surface leveling device defining a working gap adapted to drawphoto-curable liquid into the device by capillary action to create areserve of photo-curable therein, said liquid surface leveling devicebeing movable horizontally in the container to pass over a surface ofphoto-curable liquid when held in said container to form a smoothed andleveled surface layer of photo-curable liquid over a three-dimensionallaminated product that is being built up on the product table; and anirradiating head for forming a beam spot of reactive stimulation in thecontainer that corresponds to the smoothed and leveled surface layer ofphoto-curable liquid at the specified level so as thereby to cure andconvert the smoothed and leveled surface layer as a solid lamina on thethree-dimensional laminated product being built up on said producttable.
 2. A three-dimensional solid product forming apparatus as definedin claim 1 , wherein said liquid surface leveling device includes atleast one blade defining the gap for drawing the photo-curable liquid bycapillary action into a cavity defined by the at least one blade.
 3. Athree-dimensional solid product forming apparatus as defined in claim 2, wherein said blade is made of a porous material.
 4. Athree-dimensional solid product forming apparatus as defined in claim 2, wherein said blade is formed with a plurality of gaps, each defining acavity for drawing photo-curable liquid into each cavity by capillaryaction.
 5. A three-dimensional solid product forming apparatus asdefined in claim 2 , wherein said blade is shaped with verticaldepending portions that partly lie below the surface of photo-curableliquid held in the container when said product table advancesincrementally into said container during the formation of the laminatedproduct.
 6. A three-dimensional solid product forming apparatus asdefined in claim 1 , wherein said liquid surface leveling devicecomprises at least two blades arranged face to face to definetherebetween a narrow gap through which the photo-curable liquid isdrawn by capillary action.
 7. A three-dimensional solid product formingapparatus as defined in claim 6 , wherein each said blade is made of aporous material.
 8. A three-dimensional solid product forming apparatusas defined in claim 6 , wherein each said blade is formed with a numberof holes.
 9. A three-dimensional solid product forming apparatus asdefined in claim 6 , wherein said liquid surface leveling device furthercomprises a porous member interposed between said blades above the gapto absorb photo-curable liquid.
 10. A three-dimensional solid productforming apparatus as defined in claim 6 , wherein at least one of saidblades is shaped to partly depend vertically to be situated below asurface of photo-curable liquid when said product table is advance intothe photo-curable liquid by said distance equal to said specifiedthickness of a solid lamina.
 11. A method for forming athree-dimensional laminated product from a photo-curable liquid byprogressively superposing solid laminae having a specified thickness oneon top of another, each said solid lamina being provided by photo-curinga surface layer of the photo-curable liquid, said method comprising thesteps of: filling a container with a photo-curable liquid to define aworking surface; advancing a product table, on which a three-dimensionallaminated product is built up in progressive steps, into saidphoto-curable liquid incrementally step by step with each step being adepth equal to said specified thickness of said solid lamina; drawingphoto-curable liquid by capillary action into a reservoir defined in aliquid surface leveling device; moving the liquid surface levelingdevice over the working surface of said photo-curable liquid in saidcontainer to coat and smooth said photo-curable liquid over athree-dimensional laminated product that is being built up on saidproduct table; and irradiating a beam spot of reactive stimulation onsaid smoothed and leveled surface layer of said photo-curable liquid atsaid working surface to cure and convert said smoothed and leveledsurface layer as a solid lamina on said three-dimensional laminatedproduct being built up on said product table.
 12. A method as defined inclaim 11 , wherein the reservoir in said liquid surface leveling deviceincludes at least a blade.
 13. A method as defined in claim 12 , whereinsaid blade is made of a porous material.
 14. A method as defined inclaim 12 , wherein said blade is formed with a number of holes.
 15. Amethod as defined in claim 2 , including the step of sinking portions ofsaid blade below the working surface of said photo-curable liquid whensaid product table is incrementally advance into said photo-curableliquid by said distance equal to said specified thickness of said solidlamina.
 16. A method as defined in claim 11 wherein the irradiation iseffected by a He—Cd laser having a wavelength of about 325 nm.
 17. Amethod as defined in claim 11 including the further step of removing thethree dimensional laminated product from the photo-curable liquid of thecontainer, washing the removed product, and subjecting the washedproduct to a secondary hardening by irradiating with ultravioletradiation.
 18. A method as defined in claim 11 wherein only the portionsof the working surface are irradiated which correspond to the perimeterof the three dimensional laminated product being built during theformation of each lamina, and the entire portion of the working surfacecorresponding to the entire cross-section of the three dimensionallaminated product is irradiated for the first and last lamina and foreach successive X lamina, where X is a whole integer between 6 and 10.19. A method as defined in claim 11 , including the further step ofabsorbing the photo-curable liquid in the reservoir into a porous body.20. A method as defined in claim 11 wherein the entrance to thereservoir is set at approximately 1.